Question

Salut, am intampinat o problema de fizica pe care nu stiu sa o rezolv. Ma puteti ajuta?
O sarma de platina are aria sectiunii transversale s0 si lungimea l0 la temperatura t0. Platina are rezistivitatea p0 la t- si coeficientul termic a. Aflati temperatura t la care rezistenta sarmei este R
S0=0,2 mm2 l0=20m t0=20 grade C p0= 11*10^-8 ohm a=3.92 * 10^-3 grad^-1 R=53 ohm

Answer 1

$R_{0} =\rho_{0} \frac{l_{0} }{ S_{0} } =11*10^{-8} * \frac{20}{0.2*10^{-6} } =11\Omega$
$\rho=\rho_{0}(1+\alpha*t)$
$R* \frac{S_{0} }{l_{0}} =R_{0}* \frac{S_{0} }{l_{0}}(1+\alpha*t)$
$t= \frac{R -R_{0} }{ R_{0}\alpha } = \frac{53-11}{11*3.92*10^{-3} } =974 ^{o} C$